UPDATE~ I got the new battery, so tried the 1/4" and 3/8" air ratchets and they just went into skip mode and the nut barely moved. I didn't want to damage the PDC plastic slot where the stud base is captured, so I cut 2 slots into the nut with a Dremel cutting disc, put a pocket screwdriver between the base square section of the stud, and the PDC slot it's captured in to take up any slack, and used a 1/2" wrench to rock the nut back and forth. It finally came loose and backed off. To my shock what do I see? Some RED STUFF resembling nylock material, but The nut wasn't a nylock nut so I figure someone put RED thread lock on the nut when assembling. I didn't damage the threads on the stud at all so I just cleaned up everything reinstalled the cable and a new nut using a couple flat washers and di-electric grease. Everything tightened down tighter than it was before I started, so I should be good to go. I haven't completed the job yet because I'm also changing the battery terminals and it started to rain so I'll finish up tomorrow. The red thread lock was the reason it wasn't coming loose (they could have at least used blue) and it wasn't revealed until the nut was backing off the post stud. I really appreciate all the advice and suggestions from you guys, Thank you all!